• Magnesium is a macromineral that's important for many bodily actions including DNA repair, protein formation, glucose metabolization, and proper neurological function.

• Magnesium deficiency is rare for healthy adults. Those with gastrointestinal diseases, type 2 diabetes, and chronic alcoholism are more at risk of magnesium deficiency.

• Foods rich in magnesium include boiled spinach, dry roasted almonds, and cooked black beans.

• This article was medically reviewed by Xin Ma, MD, a board-certified lifestyle medicine specialist at Baylor College of Medicine.

• Visit Insider's homepage for more stories.

Magnesium is an essential mineral for good health. As the fourth most abundant mineral in the human body, "it is necessary for healthy bones, heart, muscles, and nerves. It also helps your body control energy, blood sugar, blood pressure, and many other processes," says Allie Gregg, RD, a licensed dietitian with a private practice in Kansas City, Missouri.

Here's what you need to know about what magnesium is good for, how to get enough of it, and what happens when you're magnesium deficient.

How much magnesium per day

There are two types of essential minerals the human body needs — macro and trace minerals. Magnesium is one of seven macro minerals, meaning you need relatively large amounts of it each day to stay healthy.

The amount of magnesium you need per day largely depends on your age and, as an adult, gender. Here's a breakdown, according to the National Institutes of Health:

What foods have magnesium

The mineral is found in many whole foods. Though it may be difficult to determine how much magnesium is in your food while grocery shopping because the FDA doesn't require magnesium to be listed on food labels unless that food is fortified with it.

That said, if you're following a healthy diet like the Mediterranean diet, for example, you're likely getting enough magnesium simply through the food you eat. "For example, one ounce of nuts contains about 20 percent of your daily magnesium needs," Gregg says.

Foods rich in magnesium include:

• Whole wheat bread: 2 slices provides about 12% of your daily value (DV) for an adult.

• Boiled spinach: ½ cup provides 20% DV.

• Dry roasted almonds: 1 ounce provides 20% DV.

• Cooked black beans: ½ cup provides 15% DV.

• You can also get magnesium through fortified foods and beverages like certain breakfast cereals and mineral water.

What does magnesium do

The majority — about 60% — of magnesium is present in your bones and teeth. Therefore, magnesium plays an essential role in healthy bones and teeth, and a deficiency can lead to osteoporosis and periodontal disease.

The other 40% of magnesium shows up in soft tissue in cells throughout the human body. In these cells, magnesium binds to key molecules like protein, nucleic acids, and lipids.

This binding action is what makes these molecules capable of performing their jobs including protein formation, replication and repair of DNA, proper neurological function, muscle contraction, and glucose metabolization.

That's why magnesium deficiency can increase a person's risk of a slew of diseases including type 2 diabetes, hypertension, coronary heart disease, and stroke.

Signs of magnesium deficiency

Early symptoms of magnesium deficiency, according to David Nazarian MD include:

• Muscle twitches

• Tremors

• Muscle cramps

• Nausea

• Vomiting

• Loss of appetite

• Fatigue

• Weakness

"It is very rare to have a [severe] magnesium deficiency since it is common in a lot of different foods, however, it can happen," Gregg says.

In general, healthy people aren't at risk of a severe magnesium deficiency because the kidneys restrict urinary excretion. However, specific health concerns or conditions can cause deficiency.

In particular, people with gastrointestinal diseases, type 2 diabetes, people with chronic alcoholism, as well as older adults are at greater risk of deficiency, according to the National Institutes of Health.

Related stories about diet and nutrition:

• What causes B12 deficiency and how to get enough of it in your diet

• How to get protein as a vegan from fresh, whole foods

• Why you may not be losing weight on the keto diet

• What is resistant starch and why it's healthier than simple starch

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